Electric oven



Oct. 17, 1933.

A. DAMICO ELECTRIC OVEN Filed June 13. 1931 INVENTOR fge@ B14122021) ATTORN EY Patented 1933 r n y `UN ITE 1 f y, f 1,930,836

ELoTRC'ovEN n "y Angelo D?Amico, Stockton?. Calif.

, Applicatio rape is. 193i. j serial No. 544,97 i I Y' "4fjclaings.l (or 21a-36.) 1' v This invention -relatesto electricovensgr naces andespecially to devices yof* thisy character.

`such as areadapted foriuse in eral laboratory work.

dental"v and gen- `The principal objects'oflmyinventionxareto provide an oven of this nature in whichigan `rex` tremely even and highheat may bergenerated andmaintained over the entire area of the oven.' one in which theheat will be transmitted to the ovenwchamber with a minimurnfofl less and with-fout the'heating element being actually in the chamber itself; and one in which the heatingv element is always keptwfrom' contact *with the oxygeny of thel air sogthat-there isno tendency for `it to deteriorate andl possibly burn out from this cause. q

v I have `also arranged as alunitlwith the oven an automatic and adjustable temperature control means,.solthatrthe'oven heat maybe set and held l 'at whatever temperature may. be necessary for the particular'work in hand. x .j l. t l

A furtherobject of the invention is to produce a simple andA inexpensive device and `yet one which will be@exceedingly effectivefor the pur-r pose forwhich it is designed. v

rThese objects I accomplishby means of such structure and relative arrangement of parts as will fully appear'by a perusalof the following specification andclaims; Y

4 indicate correspondingparts in the several views:

` Figslis a sectional elevation of the oven. 2

Fig. 2 is an end view o'f the oven partly in sec'* tion as on the line 2-2of Fig. 1.

chamber ycomprises `a` rectangular box-like shell 1, freely Vopened at its front end. f This'shell'is constructed as a one-piecemember of a material t having a very high fusing point and very great heat conductivity such as high'grade flreclay.

This shell is provided throughout its length with arilatspirally cut groove 2, in ywhichis, disposed a ribbon. 3 of nichrome wire -forming the heating ,element, the thickness of the ribbon being less ,than thedepth of the groove. A suitable grate G is removably mounted in the oven chamber and is arranged to support themember to be melted. The shell 1 removably ts into `a similarly Ashaped buty correspondingly larger shell `4 of 'a material having also a high` fusing point,` and made` of reclay, porcelain, or other suitable material, these twoshells constituting what is known vi-n the art as a muftle. The shell 4 is supported at its front "and back ends by one In the draWingsirnilar characters of vreference Referring now more particularly to "the'char-i" acters of reference on the drawing; the" oven" piece relatively'large'fmolded slabs 5 and 6`respe'ctivelyV made of y diatex "or other materialn having good heat vinsulating properties. The shell' i projects through the slab 5 so asto be] flush with its front face, as is also the front edge of the ovenshell. Therback end of the shell 5 however .is merelyrecessed into `the shell 6 .as shown. yThe inner shell isnot cemented to the ,outerfshell-n or permanently secured thereto yin any w'ay, so that s aid inner shell can be removed at any time if itY is `necessary to replace `the heatingribbon., i

j To -normallyhold .theinner'nshell place j againstremovall provide another molded slabf` ,7l in `front of and abutted` against the' slab 5. The slab 7 `has-an outwardly aring opening 8 ,Y whichis the same size at its inner end as the interior area of; the'oven jshell. All the vslabs are enclosed in a metal casing 9 `whichforms lthe exteriorof the oven structure; `said casing'in i cluding `a removable frontj plate 10 whosek removal exposes the slab '7 for removal.

inside' the casingfbetweenl the slabs 5 and 6 and The space the :outer` shell is `lled with va suitable" heat insulating material ,11, preferably powdered diatex.` Y i j Theplate 10 has an opening ,ofthe samesize as'that of thev opening 8 at its' outer end, andl "is covered "by a door. This door comprisesa` metal `p1atet12 hingedo'nto the plate land'a `heat insulating.r blockv 13 conforming `to the` shapegof land fitting within the opening 8. Ay

v `gas vent 14 'projectsy throughthedoor toward they top and is covered on the outside by anr adjustable valve iiap 15..l u f l y The. heat generated in the oven by the functioning of' the element is` regulated an automatically controlled as follows; y p v p Preferablyl mounted in connection with the casing at the back of the oven is valmanually ,adjustable thermostatically controlled relayv unit l6fof standard character, whosel operation is governed by a` thermostat exposed to the heat of the oven. Thisv thermostat preferably` comprisesv a fixed nichronie tube 17 projecting into the ycasing along thetop of the. outer she1l,and a carbon rod 18 inthe tube. With-this mounting of the thermostat, it is not directly subjected to the intense heat of the oven shell but to the 'lesser heat of the outer shell. It will last indefinitely therefore without deterioration While at the same time "it is sufficiently sensitive in its action for all practical purposes. The unit 16 is set for deniteoven heatsrby a rotatable dial knob 19 mounted at the front of the casing and having a shaft 20 extending lengthwise through the casing, which is connected to the unit 16 by suitable gearing 21. In this manner the setting of the relatively concealed andout-ofthe-way unit is rendered very convenient. The mechanism of the unit is of course proportioned and set so that the adjustment of the dial governs and indicates the actual heat in the oven chamber rather than the lesser heat in the zone of the 4thermostat itself.

The closing of the relay of the unit closes `a suitable switch 22 also mounted onv the back of the casing. To conceal and protect the relay and switch members, the casing is formed with a rearward extension 9a having a removable back plate 23 so that said members are rendered accessible for inspection or adjustment whenever necessary. Although these control members are mounted as a` unitary part of the oven structure, it will be seen thaty they are protected from any intense heat by the slab 6 which is between the oven and the control members, and which as previously stated is a heat insulating material.

In order to facilitate the assembly or removal of the oven shell when necessary, without tearing down the entire structure, the rear termination of the heating element is provided with a wire 24 which extends through a passage 25 cut through the back of the outer shell and the slab 6 and connects to the adjacent binding post of the switch. The front end of the element is provided with ay Wire 26 which depends through a slot 27 in the front end of the shell 4 and into a recess 28 provided in the frontend of the slab 5. This recess contains a binding post 29 to which the wire is connected and which is exposed whenever the slab '7 is removed. A' conductor 30 from the post extends through the casing to the rear end of the same, where the other wire of the circuit may be readily connected thereto as shown. It will be seen therefore that to remove the oven shell it is only necessary to resti move the front casing plate 10 and the slab '1, disconnect the wires 24 and 26 from their binding posts, and withdraw saidshell.

` Owing tothe mounting of the oven shell as above described, practically all the heat generated by the element is radiated to the interior of the oven; and the element being all around said oven a very even heat is maintained throughout its area. Also the element is nowhere exposed to the atmosphere so that the deteriorating effects due to oxidization are avoided. The element ribbon being thinner than' the depth of the groove in which it is fitted, and not being imbedded in the shell, said ribbon is free to expand without restraint and Without tending to fracture or disburb the shell.

From the foregoing description it will be readily seen that I have produced such a device as susbtantially fullls the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

1. An electric oven comprising a. muille open only on one end and forming the oven chamber, an lelectric heating element directly associated with the muille, an outer shell in which the oven shell is fit ted, relatively large heat insulating slabs in which .the ends of the outer muille are seated whereby to support said shell, a casing enclosing and supporting the slabs, and a heat insulating medium filling the casing between the slabs.

2. An electric oven comprising a shell open only on one end and forming the oven chamber, an electricheating element directly associated with the shell, an outer shell in which-the oven shell is fitted, and being removable from the front end of said cuter shell, spaced slabs in which the ends of the outer shell are seated whereby to support said shell, the forward face of the front slab being flush with the open end of the shells, another slab abutted against said front slab and having an opening therethrough the same size as that of the oven chamber, and a door over said last named slab opening.

3. A structure as in claim 2, with a casing surrounding and supporting all said slabs, anda removable front plate for said casing holding the last mentioned slab against removal; ythe door being mounted in connection with said plate.

4. An electric oven and control unit comprising a furnace chamber open at its front end, a heating element in the oven, a circuit for the element, a switch in the circuit mounted behindthe chamber in close relation thereto, an adjustable relay interposed in the circuit for controlling the switch and also mounted behind the furnace chamber, a thermostat device mounted in connection with the chamber and relay and affected by over heat for controlling the operation of the relay, and means to adjust the relay comprising a rod mounted aboveand extending along the exterior of the chamber from back to front, a

control knob onthe front end of the rod, and

connections between the back end of the rod and the adjustment mechanism of the relay.

ANGELO DAMICO. 

